1. Field of the Invention
This invention relates to a variable reluctance type angle detector having a rotor having such a shape that a gap permeance varies in a sine wave fashion with respect to an angle θ, the rotor being provided rotatably on a stator having teeth on which an excitation wire and an output wire are wound.
2. Description of the Related Art
As a conventional variable reluctance type angle detector, one having a rotor provided rotatably inside a stator has been known. The stator has a stator core having twelve teeth projecting inward and disposed in a circumferential direction, for example. An excitation wire and two-phase output wires are wound around each of the teeth.
The excitation wire is wound around each of the teeth in such a fashion that polarities of the adjacent teeth are different from each other. The excitation wire wound around the teeth forms excitation coils. The two-phase output wires are wound around each of the teeth so as to achieve a SIN output and a COS output whose phases are different from each other by 90 degrees. The two-phase output wires that are wound around the teeth form output coils. The rotor has such an outer shape that the gap permeance varies in a sine wave fashion with respect to an angle θ. When the rotor is rotated, an excitation voltage supplied to the excitation wire is outputted from one of the output wires as a COS output voltage, while a SIN voltage is outputted from the other output wire. Such variable reluctance type angle detector is disclosed in JP-A-8-178611, for example.
FIG. 5 is a diagram schematically showing one example of conventional wire structure. In the wire structure, the excitation wire and the two-phase output wires are wound around the twelve teeth. In FIG. 5, the teeth are denoted by numbers 1 to 12 sequentially along a circumferential direction. The excitation wire is positively wound around each of the odd number teeth while being negatively wound around each of the even number teeth.
The output wires output a COS output voltage and a SIN output voltage. The output wire outputting the COS output voltage is wound positively and negatively in an alternate fashion along the circumferential direction to achieve the COS output. The output wire outputting the SIN output voltage is wound positively and negatively in an alternate fashion along the circumferential direction to achieve the SIN output.
In the conventional variable reluctance type angle detector, the three layers of the excitation wire and the two-phase output wires are wound around each of the teeth. Therefore, it is necessary to secure insulation at two interlayer parts in each of the teeth. In the conventional variable reluctance type angle detector, an enamel layer is formed on surfaces of the excitation wire and the two phase output wires. With such enamel layer, the interlayer parts are insulated from one another without an insulating layer being formed between adjacent layers. However, when the parts to be insulated are increased in number, probability of insulation failure due to stripping of the enamel layer or the like is increased.